Answer:
HF
Explanation:
Hf has hydrogen bonding which is the strongest intermolecular forces. The stronger the IM forces, the higher the boiling point.
Heat is a form of energy. if the system absorbs heat/ energy it is endo thermic if it releases heat or energy it is eothermic
<u>Answer;</u>
B) water molecule has a bent shape.
<u>Explanation;</u>
- Water molecules are polar molecules because of their shape. Water molecules have one side that is positively charged due to hydrogen atom which is partially positive and the other side which is negatively charged, due to the oxygen atom.
- When two molecules get close to each other the polar forces of attraction brings them close to each other. Oxygen bonds with several hydrogen atoms in the other water molecules resulting to hydrogen bonds.
Answer: The answer is 6.78 grams.
Explanation: The equation used for solving this type of problems is:
where, 
is the initial amount of radioactive substance, N is the remaining amount and n is the number of half lives.
Number of half lives is calculated on dividing the given time by the half life.
n = time/half life
Time is given as 48.0 hours and the half life is given as 4.536 days. let's make the units same and for this let's convert the half life from days to hours.
= 108.864 hours
So, 
= 0.441
Since 5.00 g is the required amount when the radioactive substance is delivered to the scientist, it would be the final amount that is N. We need to calculate the initial amount. Let's plug in the values in the equation:
= 6.78 g
So, 6.78 g of the radioactive substance needs to be ordered.
Answer:
105 grams PbI₂
Explanation:
Pb(NO₃)₂ + 2KI => 2KNO₃ + PbI₂(s)
moles Pb(NO₃)₂ = 0.265L(1.2M) = 0.318 mole
moles KI = 0.293(1.55M) = 0.454 mole => Limiting Reactant
moles PbI₂ from mole KI in excess Pb(NO₃)₂ = 1/2(0.454 mole) = 0.227 mol PbI₂
grams PbI₂ = 0.227 mol PbI₂ x 461 g/mole = 104.68 g ≈ 105 g PbI₂(s)
